if you're on the east coast...
Movers Supply House in the Bronx has them in stock, right off 95.
New haven moving supply has a number of locations and probably stock it (CT, NJ, others).
using a 2 wheeler in place of a jbar is a bit sketchy.
I'd recommend some sort of bar that's easy to store (large pry bar) and a half dozen broom handles.
once you get a pallet or other item up an inch of the ground, scoot a broom handle (or any oak dowel) under it, you can then "high center" the item on the dowel and maneuver it. multiple dowels make it easier. and if the bottom is un-even, put 2 dowels the long way under it, and it'll either slide alot better on those or you can set yourself up with 2 levels of dowels (like this: #) and it'll roll.
fairbanks makes the best jbars I've seen. dowels and a prybar take up a lot less space than a whole jbar. easier to stash.